1. Field of the Invention
The present invention relates to a liquid dropping apparatus for a helicopter.
2. Description of the Related Art
FIG. 9 is a sectional view typically showing the structure of a liquid dropping apparatus for a helicopter according to a first conventional example.
In FIG. 9, a liquid dropping apparatus 1 for a helicopter according to the first conventional example is used for dropping water for fire fighting from a helicopter. The liquid dropping apparatus 1 has such a structure that a liquid discharge port 7 is opened on the lower surface of a water tank (hereinafter referred to as a tank) 2 attached to the lower surface of a body 4 of a helicopter 3, a dropping door 8 for opening and closing the liquid discharge port 7 by pivotally swinging around an edge portion side thereof is provided on the edge portion of the liquid discharge port 7, and the dropping door 8 is opened and closed by a torque shaft 13, a bell link 12 and a link 9 which are coupled to a driving source (not shown).
When the dropping door 8 is opened in the air in a state in which the liquid dropping apparatus 1 having such a structure is attached to the helicopter 3 and the tank 2 is filled with the water for fire fighting, the water in the tank 2 is dropped downward from the liquid discharge port 7 as shown in an arrow, thereby the fire fighting is carried out.
FIG. 10 is a sectional view typically showing the structure of a liquid dropping apparatus for a helicopter according to a second conventional example.
In FIG. 10, the liquid dropping apparatus 1 for a helicopter according to the second conventional example is constituted such that a dropping door 8 is opened and closed by parallelogrammatic links 61 and 62 differently from the first conventional example. Other points are the same as those in the first conventional example. The reference numerals 63 and 64 denote a torque shaft coupled to a driving source.
In the first and second conventional examples, a clearance formed between the lower surface of the body 4 and a ground 6 with the helicopter 3 present on the ground, that is, a ground clearance G is generally small, for example, approximately 50 cm. On the other hand, the water tank 2 has a capacity of approximately 500 to 1000 liters. Accordingly, the thickness of the tank 2 is greatly increased. In the first conventional example, therefore, the tip of the door 8 interferes with the ground 6 in a state in which the helicopter 3 is present on the ground. Therefore, the door 8 is not opened. The function of opening and closing the dropping door 8 on the ground is important for inspecting an operation before a flight and discharging the water from the tank. First of all, the helicopter 3 having the tank 2 which does not have such a function performs a duty thereof without the confirmation of a prior operation. As a result, there is a possibility that a duty achievement rate might be decreased. Secondly, in the case in which the water is discharged from the tank 2, the water should be discharged by connecting a drainage pump to the water supply port of the tank 2. Consequently, extra ground equipment is required.
In the second conventional example, as shown in FIG. 10, the door 8 is opened and closed by the parallelogrammatic links 61 and 62. Therefore, when the door 8 is to be opened, it is moved in a transverse direction along the lower surface of the tank 2. Consequently, even if the ground clearance G is small, the door 8 can be opened and closed on the ground. For this reason, the problems in the first conventional example do not arise.
However, in the case in which such parallelogrammatic links 61 and 62 are employed, the complicated mechanism causes an increase in the weight of the liquid dropping apparatus 1 and a deterioration in the reliability of a mechanism for opening and closing the door 8, which is not preferable for an airplane.
As another conventional example, moreover, the width of a liquid discharge port is reduced to decrease the swing radius of a door so that the door can be opened and closed on the ground. In such an example, the area of the liquid discharge port is reduced. Therefore, water for fire fighting cannot be dropped rapidly. In this case, a large number of liquid discharge ports are provided such that the water for fire fighting can be dropped rapidly. However, when the water for fire fighting is dropped from the liquid discharge ports, the water for fire fighting thus dropped is dispersed and changed into a mist so that the water for fire fighting is intensively dropped with difficulty. For this reason, a thickener is mixed in the water for fire fighting.
Japanese Laid-Open Patent Publication No. Hei 10-273097 (1998/273097) has disclosed a liquid dropping apparatus for a helicopter which can intensively drop water for fire fighting. The liquid dropping apparatus for a helicopter has such a structure that a tank is attached to both sides of the body of a helicopter and a liquid discharge duct of a movable type is positioned on the lower side of the body, and requires a driving mechanism for the liquid discharge duct. Correspondingly, a weight is increased and the tank is provided on the side of the body of the helicopter. Consequently, there is a problem in that the capacity of the tank cannot be increased.
In order to solve the problems, it is a first object of the present invention to provide a liquid dropping apparatus for a helicopter which is attached to the lower part of the body of a helicopter and can open and close a door in spite of a small ground clearance without increasing a weight and deteriorating the reliability of a door opening and closing mechanism.
Moreover, it is a second object of the present invention to provide a liquid dropping apparatus for a helicopter which is attached to the lower part of the body of a helicopter and can rapidly and intensively drop a liquid in a tank and can open and close a door in spite of a small ground clearance.
In order to attain the objects, the present invention provides a liquid dropping apparatus for a helicopter comprising: a tank for putting a liquid therein which is attached to a body of a helicopter to be positioned below the body, is provided with a lower surface having a concave portion formed by concaving a wall portion and has a liquid discharge port opened on a side surface of the concave portion; a door provided on a bottom surface of the concave portion of the tank to pivotally swing around a side thereof closer to the bottom surface of the concave portion, thereby freely opening and closing the liquid discharge port; and a door opening and closing means for driving the door to open and close. According to such a structure, the fulcrum as to swinging of the dropping door is raised by the depth of the concave portion. Therefore, it is possible to open and close the door of a swing type so as not to interfere with the ground in spite of a smaller ground clearance corresponding to the rise in the fulcrum. Moreover, the door of the swing type has a simple structure. For this reason, it is possible to prevent an increase in a weight and a deterioration in the reliability of the opening and closing mechanism.
In this case, the liquid discharge ports may be opened in positions of side surfaces of the concave portion which are opposed to each other as seen from above and are placed on substantially the same level; and the door may be provided in each of the liquid discharge ports. According to such a structure, the liquids discharged from the two liquid discharge ports are dropped and converge on one stream. Therefore, the change of the dropped liquid into a mist can be reduced. As a result, the liquid in the tank can be dropped intensively and a thickener is not required.
In this case, a portion of the side surface of the concave portion in which the liquid discharge port is opened may be inclined inward in the concave portion. According to such a structure, the liquids are discharged from the two liquid discharge ports obliquely downward. Therefore, it is possible to quickly discharge the liquid in the tank.
In this case, the concave portion may be formed to extend in a direction in which the body of the helicopter extends when the tank is attached to the body and the liquid discharge ports may be opened on both side surfaces in a direction in which the concave portion extends. According to such a structure, when the tank is to be attached to the helicopter for use, the liquid in the tank is discharged in a perpendicular direction to the direction of the advance of the helicopter. Therefore, the liquids discharged from the two liquid discharge ports can meet each other without the influence of the movement of the helicopter.
In this case, the tank may be formed almost symmetrically with a vertical plane extending in the direction in which the concave portion extends. According to such a structure, it is possible to prevent the stability of the helicopter from being damaged by that the tank is attached in a transverse imbalanced state.
In the above-mentioned case, moreover, a pair of convex portions may be formed on an upper surface of the tank by bulging a wall portion and may be provided such that the body of the helicopter is positioned between the convex portions when the tank is attached to the body. According to such a structure, the capacity of the tank is increased corresponding to the convex portion. Therefore, it is possible to prevent the capacity of the tank from being decreased due to the provision of the concave portion. In addition, since the water head of the liquid in the tank is increased, the liquid in the tank can be dropped rapidly.
In the above-mentioned case, furthermore, a pair of convex portions may be formed on an upper surface of the tank by bulging a wall portion and may be provided such that the body of the helicopter is positioned between the convex portions and may be almost symmetrical with the vertical plane when the tank is attached to the body. According to such a structure, the stability of the helicopter can be prevented from being damaged by that the tank is attached in a transverse imbalanced state. In addition, it is possible to prevent the capacity of the tank from being decreased due to the provision of the concave portion and it is possible to rapidly drop the liquid in the tank.
In this case, a vertical section of the concave portion in the direction perpendicular to a direction in which the concave portion extends may be formed to be substantially trapezoidal, the liquid discharge ports may be opened over substantially whole both side surfaces in the direction in which the concave portion extends respectively, an inclination of the side surfaces to a horizontal plane may be approximately 30 degrees and a width of each of the side surfaces may be substantially equal to that of a bottom surface of the concave portion. According to such a structure, the liquid in the tank can be dropped almost most rapidly.
In the above-mentioned case, the tank may be removable from the body of the helicopter. According to such a structure, the helicopter can be used for many purposes.
In the above-mentioned case, moreover, the tank may be removable from the body of the helicopter and at least one of the convex portions may be removable from other portions of the tank. According to such a structure, it can be done that one of the convex portions is removed and the tank is inserted below the body of the helicopter in a transverse direction and is attached to the body, and the convex portion thus removed is then attached to the tank. Consequently, even if the tank has the convex portion, it can be easily attached to the body.
These objects as well as other objects, features and advantages of the present invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.